Ring the changes with a fresh deal
There are two basic reasons to consider switching a mobile phone plan: money and coverage quality.
While there are dozens of variables when considering a financial motive, coverage issues are more specific to a geographical area you live in or regularly travel to. In certain counties, towns or sections of towns, there are very definite differences in the quality of mobile coverage from the three main operators.
This means that the most important factor when considering coverage is to test a phone using the operator you're considering in the area you want to use it in
Coverage quality is tested by one or two international measurement companies annually, with varying results. As a rule, Vodafone has the fastest mobile data coverage on average across the country. But Three generally offers the most data for what you pay. Therefore, if data access is your priority, it may come down to a question of quality versus quantity.
Another important factor is understanding that many other operators you can sign up to use one or other of the two big networks for their own services. For example, Virgin and Tesco Mobile both use Three's network, meaning that their coverage quality is heavily linked to what Three's network is capable of. Similarly, Postmobile uses Vodafone's network.
Eir Mobile, which used to be branded as Meteor, largely uses its own network.
Financially, the biggest winners are those switching from a very old plan to a new one. This is especially so if your plan is more than six or seven years old. Generally speaking, many of these plans cost more than €60 or €70 per month, especially if they're 'contract' plans with a phone subsidy thrown in.
In reality, you can save hundreds of euro by switching from this kind of plan to a sim-only plan with the purchase of your own phone. This is particularly the case if you don't need the very latest high-end iPhone or Samsung Galaxy. Ironically, the sim-only plan may yield more minutes and data for half the price of your old plan.
For example, a sim-only monthly mobile plan from Virgin Mobile (which uses Three's network) costs €25 per month for "unlimited" calls, texts and data in Ireland. If you purchase a good low-cost smartphone separately, like Motorola's excellent Moto G6 Play (€189 from Argos), you'll almost certainly save enough in the two years you would have spent in a contract to afford a nice iPhone the next time out.
To illustrate this, a Vodafone 'Red Connect' plan offers the same allowance for calls as the Virgin plan and less data (15GB) but costs €60 per month. The Vodafone plan includes one or two extras, such as a Spotify or Sky feature. Nevertheless, it's €420 more expensive, or €660 more expensive over a two-year period, including the cost of the Moto G6 phone.
How to switch... Mobile phone providers
STEP 1 Wait until your current contract plan is up
STEP 2 Change to a sim-only plan
STEP 3 Buy a reasonably-priced smartphone upfront
Potential savings: €660
Total time: Depends on remainder of contract